1. Field of the Invention
The present invention relates to a laser apparatus.
2. Description of Related Art
There is known a laser apparatus which is provided with a mechanism for cooling a laser light source since the laser light source generates heat. In particular, a high power laser apparatus uses a cooling water to cool the laser light source. However, when air having a high humidity contacts the portion which has been cooled by the cooling water and whose temperature has been lowered, waterdrops adhere thereto due to dew condensation. The waterdrops may result in a breakdown of the laser apparatus.
For instance, in a laser apparatus using a laser diode as the light source, a drive voltage is applied to micro elements, and accordingly, the internal electric field intensity is large. If a waterdrop adheres to an electrode, etc., of the laser diode, a short circuit easily occurs, so that there may be a critical damage to the laser diode. Furthermore, in a carbon dioxide laser apparatus, a high voltage is applied in order to oscillate a laser light. Therefore, if dew condensation occurs in the laser apparatus, a spark may occur and may damage electrodes or peripheral parts. In addition to the foregoing, if a water drop adheres to each part of the laser apparatus, the parts are contaminated or corroded, thus possibly resulting in a significant reduction of reliability.
Japanese Patent No. 5651396 discloses a fiber laser oscillator in which a laser light source and a fiber laser module are supplied with dry air to be dehumidified. Japanese Patent No. 3338974 discloses a laser apparatus comprising a first cooling water passage provided in a laser oscillation part, a second cooling water passage provided in laser power supply part, a heat exchanger for controlling the temperature of the cooling water, and a pump which supplies the cooling water to the first cooling water passage and the second cooling water passage.
Japanese Unexamined Patent Publication No. 2001-326410 discloses a cooling apparatus for a semiconductor laser, comprising a heat sink in contact with a stack of laminated laser diode bars, and a coolant supply mechanism which supplies cooling water to an internal coolant passage of the heat sink. In this cooling apparatus, whether or not the temperature of the stack is approximate to a value at which a dew condensation occurs is judged to control the flow rate of the cooling water supplied to the coolant passage.
Cooling apparatuses comprising a Peltier element are also known other than those comprising a compressor. For example, Japanese Unexamined Patent Publication No. 2015-12063 discloses an image output apparatus such as a projector comprising a first Peltier element arranged in a first region including a light source device and a second Peltier element arranged at a position spaced from a second region including an optical window to be prevented from the occurrence of dew condensation. In this image output device, the first region is cooled by the first Peltier element and a third region in proximity to the second Peltier element is cooled by the second Peltier element.
In the internal space of the laser apparatus, the temperature increases due to heat radiated from heat generating components or heat transmitted from the outside to the inside of the laser apparatus in accordance with an increase of the environmental temperature or the like. In the laser apparatus, the heat generating components can be cooled by cooling water. As is well known, the laser apparatus is provided with an air-cooling type panel cooler which supplies cooled dry air to the inside of the apparatus to prevent dew condensation from occurring during cooling by the cooling water. The panel cooler can suppress an increase of the internal temperature of the laser apparatus by the heat generating components and lower the dew point of the internal air of the laser apparatus.
However, if a panel cooler and a cooling device using a cooling water are used together, when the environmental temperature increases, the quantity of heat transmitted from the outside increases, but the cooling capacity of the panel cooler decreases. Because of this, it is necessary for the panel cooler to have sufficient leeway with respect to cooling capacity, that is, a large panel cooler must be used, thus leading to an increase of the size of the laser apparatus. Furthermore, an air-cooling type cooler must be provided with an air intake port and foreign matter may enter the inside of the laser apparatus. Consequently, problems with maintenance of the inside of the laser apparatus, the reliability or appearance of the laser apparatus may be caused.
Moreover, depending on the environment in which the laser apparatus is arranged or the season, there are cases where the temperature of the cooling water is too low. In such cases, if cold cooling water is supplied when the laser apparatus begins operating, there is a risk of dew condensation occurring. To prevent this, inconveniently, the laser light source cannot be driven until the temperature of the cooling water reaches a predetermined temperature. Namely, there is a drawback that it takes time to start the operation of the laser apparatus.